Circuit controlling device



Aug. 28, 1934. A. w. KRIEGER CIRCUIT CONTROLLING DEVICE Filed Oct. 26,1955 2 Sheets-Sheet 1 f5 Warffum llllln 1934. A. w. KRIEGER 1,971,614

CIRCUIT CONTROLLING DEVICE Filed Oct. 26, 1935 2 Sheets-Sheet 2 PatentedAug. 28, 1934 1,971,614 CIRCUIT (TONTROLLINGl DEVICE Alvin W. Krieger,Milwaukee, Wis., assigner to Cutler-Hammer, Inc., Milwaukee, Wis., acorporation of Delaware Application October 26, 1933, Serial No. 695,33620 Claims. (Cl. 201-56) This invention relates to improvements incircuit controlling devices, and more particularly to improvements inrheostats for control of relatively low voltage circuits.

5 An object of the invention is to generally improve and simplify thedetails of construction and assembly of the parts of devices of theaforementioned chaiacter.

y Another object is to improve the operating characteristics of suchdevices.

Another object is to provide a novel form of actuating shaft for themovable contactor of the device.

Another object is to provide an improved form v of insulating operatingknob for cooperation with an actuating shaft of the characteraforementioned..

Another object is to provide improved means for supporting and coolingthe rheostat resistor.

Another object is to provide an improved form of combined rheostat andindicating light.

Another object isto provide a novel arrangement of the indicating lightsupporting elements with respect to the rheostat parts.

Another object is to standardize a maximum number of the parts employedin constructing rheostats both with and without associated indicatinglights.

Other objects and advantages 30 will hereinafter appear.

of the invention The accompanying drawings illustrate certainembodimentsof the invention which will now be described, it being understood thatthe embodiments illustrated are susceptiblel of modification in certaindetails thereof without departingI from the scope of the appendedclaims.

In the drawings, Figure 1 is a top plan View of arheostat with anindicating light, as constructed in accordance with my invention,-theclamping nuts of Fig. 2 being omitted for purposes of illustration.

Fig. 2 is a verticalsectional view on the line 2-2 of Fig. 1,-theelectric lamp being omitted.

Fig. 3 is a bottom plan view of the device illustrated in Figs. 1 and 2.

Fig. 4 is a horizontal sectional view on the line 4--4 of Fig. 2.

Fig. 5 is a vertical sectional view on the line 5--5 of Figll,--the'lamp being shown in position, the operating knobV and clampingnuts being omitted, and the actuating shaft having been rotatedclockwise through an angle of approximately 120 degrees from theposition thereof shown in Figs. 1 and 2.

Fig. 6 is a lhorizontal sectional view on the line 6-6 of Fig. 2,-thebushing and the actuating shaft only being illustrated.

Fig. 'l is a top plan view of a form of rheostat without an indicatinglight, as constructed in accordance with my inventionthe usual clampt*ing nuts being omitted for clarity of illustration.

Fig. 8 is a vertical sectional view on the line 8-8 of Fig. '1.

Fig. 9 is an enlarged fragmentary sectional view on the line 9-9 of Fig.8.

Fig. 10 is a perspective view, in separated relation, of certain of theparts shown in Figs. 7 and 8,-a portion of the operating knob beingbroken away.

Fig. l1 is a side elevational view oi. a rheostat like that shown inFig. 8,-'-a portion of the rheostat being shown in vertical section toillustrate a modified form of device for indicating to the touch thecircuit making and circuit breaking positions of the contactor, and

Fig. l2 is a perspective view, in separated relation oi the parts of thedevice illustrated in Figs. 1 to 6,-the clamping nuts of Fig. 2 beingomitted.

In all figures of the drawings, except Fig. 9, a scale of one andone-half times normal size is employed,-Fig. 9 being drawn to a scale ofapproximately three times normal size.

Referring rst to Figs. 1 to 6 and 12, the numeral 15 designates ahousing formed of a single piece of sheet metal, said housing being oin- 35 verted cup-shape. The upper end of said housing is slightlydepressed to provide a flat portion 16 of circular contour, said atportion 16 being prou vided with a substantially circular opening 1'7within which the reduced lower end 18 of an externally threaded hollowmetal bushing 19 is adapted to fit,-said end 18 being upset over theinner surface of the housing (as shown in Figs. 2 and 5) to rigidly andpermanently secure thelatterand said bushing to each other.

Bushing 19 is provided with the usual vertical groove 20 to accommodatethe key or lug formed4 upon a suitable dial or indicating plate (notshown). For purposes of my invention it is necessary to insuresecurement of the bushing 19 and housing 15 in a given rotaryrelationship to each other, and accordingly the housing l5 is providedwith an integral lug 21 which is adapted to flt into the aforementionedgroove 20, as best illustrated in Fig. 2. Whilev upsetting of the lowerend 18 of the bushing is normally sufficient to prevent relativerotation thereof with respect to housing 15, thel engagement of lug 21with the walls of groove 20 will additionally and positively insureagainst relative movement of said parts.

Gli

'I'he actuating shaft 22 of the rheostat is of split tubular form,thesame preferably consisting of a punched and stamped sheet metal platewhich is bent to the shape best illustrated in Fig. 12. Shaft 22 isprovided adjacent to the upper edge thereof and adjacent to the split 23with an integral boss or projection 24 of the form illustrated in Figs.2 and 12. In a predetermined plane below the plane of boss 24, andpreferably in 'vertical alinement with the latter, isa lug 25 sheared atthe bottom and sides thereof from shaft 22 and bent outwardly withrespect thereto, whereby upon downward insertion of said shaft intobushing 19 the lower edge of lug 25 will engage the upper end of thebushing to insure exposure of a given portion of the upper end of theshaft.

The arrangement is preferably such that the main body of the lower endof shaft 22 is located substantially iiush with the lower end of saidbushing,rsaid shaft being provided with a pair of diametrically opposedintegral lugs 26 and 27 which extend below said bushing. I provide aflat punched plate 28 of insulation, said plate having openings 29 and30 through which the respective lugs 26 and 27 are adapted to extend,said lugs being bent inwardly toward each other over the lower surfaceof said plate, as shown at 27 in Fig. 2 and as indicated in dotted linesin Fig. 4. I

- Plate 28 is provided on its upper face with a center lamp contact 31and on its lower face with a rheostat contactor 32, said contact andsaid contactor being formed of a resilient or springy metal, and the-same being mechanically connected to plate 28 and electricallyconnected with eachother as by means of an eyelet 33 (see Fig. 12).After attachment of said parts to plate 28 the free end of contact 31 isbent or reexed along the dotted line 31B (Fig. 12), said contact endhavingan angularly extending lug or nib 31b to prevent excessive bendingthereof by the center contact of a lamp as best illustrated in Figs. 2and 5. The free end of contactor 32 is angled downwardly with respect toplate 28, and

the same is provided with apair of substantially parallel ears 32a, 32bwhich ext'end upwardly into the plane of plate 28,-the latter beingprovided with a notch or cut-away portion 34 to provide` clearancetherefor.

Upsetting of eyelet 33 will ordinarily prevent rotary movement of plate28 relatively to'contactor 32, and as best illustrated in Fig. 5 thewalls of notch 34 will cooperate with saidears 328, 32b to furtherinsure against such relative movement.

In order to-insure a proper electrical connection between shaft 22 andbushing 19 I .prefer -to interpose between plate 28 and the lower end ofsaid bushing a metal ring or washer 35 of the form best illustrated inFig. 12, said ring having notches 35B, 35'? to accommodate with a snugfit the aforementioned lugs 26 and 27, and the latter when bent vin themanner aforedescribed being adapted to drawaid ring fairlytightlyagainstthe lower endfshaft 22 and into frictional or sliding engagementwith the lower end of bushing 19. Other means might be employed toinsure proper electrical engagement between shaft 22 and bushing 19, asby extending outwardly from the former one or more lugs or bosses tovresiliently engage the inner surface of the latter.

As shown in Figs. 2 and 12 the shaft 22 is provided at the upper endthereof with a vertical notch 36. Shaft 22 is provided with a pluralityof lugs partially sheared therefrom and bent inwardly, as indicated at37, 38 and 39, said lugs being angularly and vertically spacedrelatively to each other to cooperatively engage the thread upon thescrew shell contact 40 of a suitable electric lamp the major portion ofthe bulb 41 of which is adapted to be positioned within the shaft 22. Inthe particular form of the device as illustrated the diameter of thescrew shell contact 40 is substantially less than the internal diameterof shaft 22, and accordingly I prefer to provide the latter with aplurality of inwardly pressed beads or ridges 42, 43 and 44, whereby thelamp will be properly centered with vrespect to said shaft.

The operating knob of the device preferably comprises a hollow moldedinsulating member 45 which is adapted to telescope onto the upper end ofshaft 22, said knob having a notch 45a in the lower edge thereof forcooperation with the bossV 24 and lug 25 aforementioned to, insureassembly in only one rotary relation of said parts. Due to the presenceof the slit 23 in shaft 22 the latter is rendered compressible to anextent suicient to permit the irmer wall of member 45 to pass downwardlyover boss 24, said inner wall being provided with a depressionv orundercut. 45a into which said boss is adapted to snap to releasablyrestrain member 45 and shaft 22 against separation. The inner wall ofmember 45 is further provided with an integral flatsided rib 45 whichfits into the notch 36 in the upper end of said shaft to positivelyrestrain the latter and said member 45 against rotary movementrelatively to. each other.

The recess in member 45 is sufficiently large to provide clearance forthe projecting upper end of lamp bulb 41. Inasmuch 'as the lamp bulb isentirely enclosed by the shaft 22 and member 45 I mold the latter frominsulating material of translucent character. Electrical insulatingmolding compositions 'having the aforementioned characteristics are wellknown in the artA and need not be described in detail herein. Incarrying out my invention, however, I prefer to mold the member 45 withanupper end wall at least certain portions or areas 45d of which arerelatively thin to permit ready passage of light rays from the lamp whenthe latter is illuminated. Also I prefer to provide in said upper endwall a relatively thick portion or portions 45.- said thick portionpreferably being in the form of a suitable outline or indicator which isthrown into accentuated relief with respect to the relatively thinportionlwhen the lamp is lit. The periphery of knob 45 is preferablygrooved or otherwise roughened as indicated at 45f to facilitate manualoperation thereof. l

The housing 15 is preferably provided with a pluralityof integral lugs46, 47, 48 and 49,one of said lugs 46 bei'ngof a width or size dierentfrom that of the other lugs. I also employ a fiat. punched insulatingplate 50 which is provided with peripheral notches 51, 52, 53 and 54 toregister.- respectively with the lugs 46 1:0149 aforementioned-said lugsbeing bent inwardly over the lower surface of said plate to retainthelatter in assembled relation to the housing. Plate 50 dissipation of theheat generated vviding clearance length of multiple-strand copper wirehaving a covering of asbestos fibers. Said core willassist in supportingthe individual turns of the helix, and the same also acts to increasethe rate of in the resistor. The helix is bent to arcuate form asillustrated, and a coil at one end thereof is bent to provide anattaching loop 60"I which lies in the plane of the lower surface of thehelix. Said helix is positioned upon the upper surface of plate 50 withloop 60 in registry with the aforementioned opening 56, and a terminalplate 62 is positioned upon the lower surface of plate 50 with itsopening 62 (Fig. 12) in registry with said opening 56. An eyelet 63 isthen passed through loop 60a and openings 56 and 62a and then upset tosecure said terminal plate and one end of helix 60 to plate 50 and toelectrically connect the same with each other. Plate 62 is provided witha tapped opening 62b to receive the usual binding screw S22- the opening55 in plate 50 profor the shank of said screw. Helix 60 is provided atthe other end thereof with an uncoiled portion 60b which is inserteddownwardly through opening 59, said end being bent over the lower` faceof plate 50 and then cut by means of a suitable tool to the lengththereof 4shown in Fig. 3. To insure against distortion of helix 60 fromthe arcuate form thereof illustrated I prefer to employ an additionalfiat punched plate 64 of insulation,the same being superimposed uponplate 50 and having an arcuate slot 64a to accommodate the helix and torestrain the latter against substantial movement in a horizontal plane.Plate 64 is notched as indicated at 64b to provide clearance for theshank of screw 62, and said plate is further provided with a pair 'ofopenings 64 and 64d to register with the aforementioned openings 57 and58.

superimposed upon plate 64 isa resilient metal member 65, the samehavinga horizontal portion provided with an opening 65B. An eyelet 66 isadapted to penetrate the openings 65a, 64

and 57 and an opening 67a in a terminal plate 67 located upon the lowersurface of plate 50, said eyelet having one end thereof upset to retainall of said parts in assembled relation. Terminal plate 67 is providedwith a tapped opening 67b to receive the usual binding screw 67c,-the

openings 58 and 64d in plates 50 and 64 respectively affording clearancefor the shank of said screw. Member 65 is provided with an arm 65boffset upwardly fromgbase 50 and said arm comprises a vertical portionhaving a reduced and shouldered upper end 65,-the reduced end of whichis adapted to fit into the opening ineyelet 33 and the shoulders ofwhich are adapted to bearagainst the lower end -of said eyelet (see Fig.2) to provide an'electrical connection be- V tween the terminal plate 67and the rheostat contactor 32 and center 'lamp contact 31.

- Member 65 is provided with a second arm 65d v' which is reexed toextend upwardly and then inwardly into frictional lower surface -ofplate28 (see Fig. 2). The end of rei'lexed arm 65d' is provided with anupwardly extending boss or 'projection 65e which is adapted to snap intoand flt snugly between the walls of the respective notches 28and 28h.The arrangement is such that when knob 45 is moved in acounter-clockwise direction to the position thereof indicated in Fig. 1said boss 65 will snap into engagement with the walls of notch 28 inplate 28 to indicate to the touch that the rheostat contactor has beenmoved entirely out of engagement engagement -with the 73b in the upperedge with the rheostat resistor 60 wherebythe circuit of the controlledmotor and the circuit of lamp 41 are interrupted. Upon a slight movementof knob 45 in a clockwise direction from the position thereof lastmentioned the boss 65 will snap into engagement with the walls of notch28b to indicate to the touch that the rheostat contactor 32 is engagedwith resistor 60 at a point closely adjacent to the point of connectionof the latter to terminal plate 62, whereby substantially full voltageis applied to the motor terminals to insure starting thereof. After themotor (not shown) has been started the speed thereof may be reducedgradually by continued movement of knob 45 in a clockwise direction toincrease the amount of the resistance of resistor v6() included in themotor circuit.

In order to positively limit the degree of rotation of knob 45 and itsassociated parts in each direction, I prefer to provide upon plate 28 apair of integral radial shoulders 28 and 28darranged in spaced relationto eachother on opposite sides of the aforementioned notch 34,-theshoulder 28c being adapted to engage a lug 15 (sheared and struckdownwardly from the upper end of housing 15) when the parts are in thecircuit breaking position thereof, and the shoulder 28d being adapted toengage said lug 15* when the parts are rotated to their opposite extremeposition wherein substantially all of the resistance of resistor 60 isincluded in the controlled circuit. Housing 15 is provided with amultiplicity of openings 15b to afford ventilation and cooling of therheostat resistor.

In practice one terminal 'of the controlled motor 110 is connected withterminal plate 67, and one terminal of the battery is connected withterminal plate 62,-the other terminals of the motor and battery and themetal bushing 19 being grounded in the usual manner. The device hereindisclosed 115 is particularly applicable to the control of fractionalhorse-power motors such as are employed for driving the fans ofhot-water-type heaters for' automobiles. To install the device a singlehole may be provided in the dashboard of an automo- 120 bile, and afterattaching the proper circuit wires to the terminal plates 62 and 67 theknob 45 and one of the clamping nuts 68 are removed,-the nut 69 beingproperly adjusted to correspond with the thickness of the dashboard.After insertion of 125 the bushing 19 through the hole from the reartoward the front of the dashboard the nut 68 is applied to clamp thedevice in position and the knob 45 is then applied to the outer end ofthe shaft 22 by a straight-line telescoping movement. 130

In the device illustrated in Figs. 7 and 8 the' insulating plates 50 and64 and the parts carried thereby are identical with those aforedescribedand the samehave been given corresponding characters of reference. Thehousing 70 may be 135 formed. from a metal blank identical with thatemployed for formation of housing 15. However, the opening 71 in housing70 is made relatively small to accommodate the reduced lower end of' theexternally threaded 72.-said bushing having a vertical groove 'I2n andhousing 70 having a lug 70* to cooperatively engage the same. Therelatively small tubular shaft 73 is provided with a vertical slit 73, anotch thereof, and an outwardly 145 extending lug 73c and'boss 73dcorresponding to the lug 25 and boss 24 aforedescribed. Shaft 73 is'provided at its lower end with a'pair of diametrically opposed lugs(Fig. 8)

'73 (Fig. 10) and '13l hollow metal 'bushing 140 As will be understoodthe lugs 73e, 73i of shaft 73 are less widely spaced than theaforementioned lugs 26, 27 of shaft 22,-and the at punched insulatingplate 74 is provided with openings (not shown) to register with lugs73e, 73f. Said lugs are bent away from each other over the lower face ofplate 74, as indicated at 73f in Fig. 8, to provide clearance betweenthe same and the rheostat contactor 32. An eyelet 33 like thataforedescribed may be employed to secure contactor 32 to plate 74. Plate74 is otherwise identical with the plate 28 aforedescribed, the samehaving a peripheral notch 74e (corresponding with notch 28B) to receivethe boss 65e of arm 65d of member in the circuit breaking position ofthe parts, and said plate being provided with a notch to receive theupwardly extending ears of contactor 32, a notch corresponding withnotch 28b aforedescribed, and shoulders corresponding with the shoulders28, 28d of plate 28. Housing 70 is provided with a sheared anddownwardly struck lug b to cooperate with the shoulders on plate 74.Housing 70 is provided with lugs corresponding in size and function withthe lugs 46 to 49 aforedescribed (see 46, Fig. 8, and 49, Fig. 11).

The knob need not be composed of translucent insulating material, andaccordingly I prefer to mold the same from a phenol formaldehydecondensation product. Knob 75 is recessed to accommodate the upper endof shaft 73,-the same having'a projection 75a to enter the notch 73h, anotch 75b and depression 75c to accommodate the lug 73 and boss 73drespectively, and a grooved or roughened periphery 75d to facilitatemanipulation thereof. The upper surface of knob 75 may have adepression, of the character indicated at 75e formed therein, saiddepression being preferably lled or coated with white enamel or othermaterial having a distinguishing color as compared with the color ofsaid knob 75. Ventilating openings 70may be provided in the housing 70.V

The manner in which the boss 65e snaps into engagement with the notch74B, for instance, is shown in enlarged detail in Fig. 9.

In the modification shown in Fig. 1l most of the parts are substantiallylike those shown in Figs. 7 to 10 and have been given correspondingnumerals. of reference. In Fig. 11, however, the member 65 is notprovided with the reiiexed arm 65d aforementioned; but instead thereof abolt 76 has its shank slidable within the opening in eyelet 66,-therounded upper end 76a of said bolt being biased by a coiled compressionspring 77 into engagement with the walls of a notch 78a provided in theflat punched insulating plate '78,4aid notch 78B (corresponding with theoii position of the rheostat) and the other notch (corresponding withthe initial circuit making position of the rheostat) extending radiallyinwardly to a slightly greater extent than the notches 74a (Fig. 8) and28a, 28b (Fig. 12) aforedescribed. The spring 77 is of substantiallyconical shape as illustrated to provide for employment of a wire of therequired size in formation thereof while permitting compression of thehelix without interference between the respective turns thereof.Moreover the enlarged lower end of spring 77 permits the same tosurround the flange at the upper end -of eyelet 66 whereby employment ofa spring having the desired vertical dimension when compressed ispermitted.

What I claim as new and desire to secure by Letters Patent is:

1. In a rheostat, in combination, an inverted cup-shaped sheet metalhousing, a flat punched Lavinia plate of insulating material againstwhich the lower edge of said housing is adapted to seat, said platehaving a plurality of peripheral notches, one of said notches being ofgreater width than other of the same, said housing having acorresponding number of lugs so shaped as to provide for a t thereofwithin said notches in only one rotary relation of said parts, said lugsbeing bent inwardly over the lower face of said plate to retain the samein assembled relation to said housing, a helical resistor wire arcuatelyarranged upon and secured to the upper face of said plate, a pair ofwiring terminal members positioned upon the lower face of said plate,one of said terminal members being electrically connected with one endof said resistor Wire, an externally threaded hollow metal bushingsecured to the upper end of said housing, a hollow shaft penetratingsaid bushing and having portions thereof projecting from each end of thelatter, a flat punched plate of insulating material to which the lowerend portion of said shaft is permanently connected to provide fordriving of the former by the latter, a contactor biased into the planeof said resistor wire, an eyelet penetrating said contactor and saidlast mentioned plate to secure the same against rotary movementrelatively to each other, a metal member having a reduced end portionresiliently engaging the walls of said eyelet and means forelectricallyI and mechanically connecting said metal member with theother of said terminal members.

2. In a rheostat, in combination, an inverted cup-shaped sheet metalhousing, a flat punched plate of insulating material against which thelower edge of said housing is adapted to seat, said plate having aplurality of peripheral notches, one of said notches being of greaterwidth than other of the same, said housing having a corresponding numberof lugs so shaped as to provide for a fit thereof within said notches inonly one rotary relation of said parts, said lugs being bent inwardlyover the lower face of said plateto retain the same in assembledrelation to said housing, a helical resistor wire arcuately arrangedupon and secured to the upper face of said plate, a pair of wiringterminal members positioned upon the lower face of said plate, one ofsaid terminal members being electrically connected with one end of saidresistor wire, an externally threaded hollow metal bushing secured tothe upper end of said housing, a hollow shaft penetrating said bushingand having portions thereof projecting from each end lof the latter, aflat punched plate of insulating material to which the lower end portionof said shaft is permanently connected to provide for driving of theformer by the latter, a contactor biased into the plane of said resistorwire, an eyele/t penetrating said contactor and said last mentionedplate to secure the same against rotary movement relatively to eachother, a metal mem- .ber having a reduced end portion resilientlyengaging the walls of said eyelet, means for electrically andmechanically connecting said metal member with the other of saidterminal members, means providing for resiliency of the upper end of.said shaft, a molded hollow insulating knob, said knob and said shaftbeing formed to provide a snap catch therebetween upon telescopingthereof, and means-formed integrally with said knob and said shaft topositively insure against rotation thereof relatively to each other.

3. In a device of the-character described, in

combination, an inverted cup-shaped sheet metal housing, an externallythreaded hollow metal bushing rigidly and permanently secured to theupper end of said housing, a cylindrical hollow shaft formed ofresilient metal, said shaft having a vertical slit extending throughoutthe length thereof, said shaft being insertable downwardly through saidbushing and having a lug struck outwardly therefrom to engage the upperend of said bushing, said shaft having a plurality of lugs formedintegrally therewith and adapted to project beyond the lower end of saidbushing, a flat punched plate of insulating material having openings toaccommodate said last mentioned lugs and over the lower face of whichthe latter are bent to retain said parts in assembled relation, a metalmember secured to saidplate and having a resilient arm extendingradially of the latter to provide a contactor, a helically woundresistor wire with which said contactor is adapted to engage, aninsulating base upon which the helical resistor is supported in arcuateformation, a pair of wiring terminal elements exposed upon the lowersurface of said base, one of said terminal elements being electricallyconnected with one end of said resistor, and means providing anelectrical connection between the other of said terminal elements andsaid contactor. e

4. In a device of the character described, in combination, an invertedcup-shaped sheet metal housing, an externally threaded hollow metalbushing rigidly and permanently secured to the upper end of saidhousing, a cylindrical hollow shaft formed of resilient metal, saidshaft having a vertical slit extending throughout the length thereof,said shaft being insertable downwardly through said bushing and having alug struck outwardly therefrom to engage the upper end of said bushing,said shaft having a plurality of lugs formed integrally therewith andadapted to project beyond the lower end of said bushing, a flat punchedplate of insulating material having openings to accommodate said lastmentioned lugs and over the lower faceof which the latter are bent toretain said parts in assembled relation, a metal member rigidly securedcentrally of said plate and having a resilient arm extending radially ofthe latter to provide a contactor, a helically wound resistor wire withwhich said contactor is adapted to engage, an insulating base upon whichthe helical resistor is supported in arcuate formation, a pair of wiringterminal elements exposed upon the lower `surface of said base, one ofsaid terminal elements being electrically connected with one end of saidresistor, means providing an electrical connection between the other ofsaid terminal elements and said contactor, a molded insulating knobhaving va substantially cylindrical recess to accommodate the upper endof said shaft, and said upper end of said shaft and the walls of saidrecess being cooperatively formed to provide for telescopic engagementthereof with a snap action in only one rotary relation of said parts andto restrain said parts against rotation relatively to each other.

5. In a device of the character described, in combination, an invertedcup-shaped sheet metal housing, an externally threaded hollow metalbushing rigidly and permanently secured to the vupper end of saidhousing, a cylindrical hollow shaft formed of resilient metal, saidshaft having a vertical slit extending throughout the length thereof,said shaft being insertable downwardly through said bushing and having alug struck outwardly therefrom to engage the upper end of said bushing,said shaft having a plurality of lugs formed integrally therewith andadapted to project beyond the lower end of said bushing,

a flat punched plate of insulating material having openings toaccommodate said last mentioned lugs and over the lower face of whichthe latter are bent to retain said parts in assembled relation, a metalmember rigidly secured centrally of said plate and having a resilientarm extending radially of the latter to provide a contactor, a helicallywound resistor wire with which said contactor is adapted to engage, aninsulating base upon which the helical resistor 'is supported in arcuateformation, a pair of wiring terminal elements exposed upon the lowersurface of said base, one of said terminal elements being electricallyconnected with one end of said resistor, means providing an electricalconnection between the other of said terminal elements and saidcontactor, a molded insulating knob having a substantially cylindricalrecess to accommodate the upper end of said shaft, said upper end ofsaid shaft being provided with a boss and a notch and the walls of saidrecess being provided with a depression and a projection to respectivelycooperate with said boss and said notch to provide for telescopicengagement of said knob and said shaft with a snap action in only onerotary relation of said parts and to restrain said parts againstrotation relatively to each other, said knob having an indicatingelement formed upon the upper surface thereof and arranged in a givenrotary relation to said depression and said projection.

li 6. In a rheostat, in combination, a iiat punched plate of insulation,a pair of wiring terminal elements positioned upon the lower face ofsaid plate, a helically wound resistor wire arranged in arcuateformation upon the upper face of said plate and having the ends thereofsecured to said plate, one of said ends being electrically connectedwith one of said terminal elements, a relatively smaller flat punchedplate of insulation superimposed upon said first mentioned plate andhaving an arcuate slot to accommodate said helix, the Walls of said slotcooperating with said helix to prevent substantial displacement thereofrelatively to said first mentioned plate, a metal member positioned uponthe upper face of said second mentioned plate, said member having aportion thereof bent upwardly at an angle to said second mentioned plateto provide a resilient arm, Asaid arm having a. reduced and shoulderedend portion located substantially centrally of said plate and extendingupwardly at substantially a right angle thereto, and an eyeletpenetrating said member, said plates and the other of said terminalelements to secure said parts in assembled relation to each other.

7. l'n combination, a resistor consisting of a wire composed of an alloyof nickel and chromium, said wire being wound into the form of a helixhaving the turns thereof slightly spaced from each other, an insulatingbase upon which said helix is arranged in arcuate formation and to whichthe ends thereof are attached, and a core located within said helix andsupported by the latter, vsaid core acting to resist endwise move- 4mentof the respective turns of said helix relativefrom each other, aninsulatingbase upon which said helix is arranged and to which the endsof said helix are attached, a core located within said helix andsupported by the latter, said core acting to resist endwise movement ofthe respective turns of said relix relatively to each other and toassist in dissipating the heat generated by said helix, said corecomprising ay Amultiple-strand copper wire having an asbestos coveringformed thereon, a pair of wiring terminal elements located upon thelower surface of said base, one of said wiring terminal elements beingmechanically and electrically connected to one end of said helix, asingle-arm contactor cooperable with said helix and supportedindependently of said base, and means comprising a resilient conductoradapted to provide. an electrical connection between said contacter andthe other of said terminal elements.

9. In a rheostat for control of relatively low voltage circuits, .incombination, an inverted cupshaped sheet metal housing, said housinghaving in the top'thereof a relatively large central opening and amultiplicity of relatively smaller openings surrounding said centralopening, an externally threaded hollow metal bushing, said bushinghavinga reduced lower end portion inserted into said opening and upset overthe inner surface of said housing, said bushing having a vertical grooveand said housing having a lug positioned within said groove topositively restrain said parts against relative rotation, a punched andstamped sheet metal plate, said plate being bent to provide alongitudinally split shaft'of substantially cylindrical form, said shafthaving a lug struck-outwardly therefrom adjacent to said split andengageable with the upper end of said bushing to insure exposure of agiven length of the upper end portion' of said shaft, said shaft havinga boss formed thereon in a plane above the aforementioned lug and anotch extending downwardly from the upper edge thereof, a molded'insulating knob having a recess to accommodate the upper end of saidshaft, said knob having a notch in the lower edge thereof forcooperation with said lug to guide said parts into proper telescopicengagement with eachother, the wall of said recess having a depressionformed therein to accommodate said boss whereby said parts are engagedwith a snap action, and the wall of said recess also having a projectionformed -integrally therewith for cooperation with the notch in saidshaft, whereby'said knob and said shaft are positively restrainedagainst rotation relatively to each other. i

10. In a rheostat -for control of relatively lowV voltage circuits, incombination, an inverted cupshaped sheet metal housing, said housinghaving in the top thereof a relatively large central opening and amultiplicity of relatively smaller openings surrounding said centralopening, an externally threaded hollow met'al bushing, said bushinghaving a reduced lower end portion inserted into said opening and upsetover the inner surface of said housing, said bushing having a verticalgroove and said housing having a lug positioned within said groove topositively restrain said parts against relative rotation, a punched andstamped sheet metal plate, said plate being bent to pro-l sitionedwithin said said lugs -are bent to positively Lavinia in the lower edgethereof for cooperation with said lug to guide said parts into propertelescopic engagement with each other, the wall of said recess having adepression formed therein to accommodate said boss whereby said partsare engaged with a snap action, the wall of said recess also having aprojection formed integrally therewith for cooperation with whereby saidknob and said shaft are positively restrained against rotationrelatively to each other, said shaft having a pair of lugs formedintegrally with the lower end thereof and adapted to extend below saidbushing, and a nat punched plate of insulation having openings toaccommodate said lugs and over the lower surface of which said lugs arebent to positively restrain said shaft and said bushing againstsubstantial movement longitudinally of each other.

11. In a rheostat for control ofrelatively low voltage circuits, incombination, an inverted cupshaped sheet metal housing, said housinghaving in the top thereof a relatively large central opening and amultiplicity of relatively smaller openings surrounding said centralopening, an externally threaded hollow metal bushing, said bushinghaving a reduced intol said opening and face of said housing, saidbushing having a vertical groove and saidhousing having a.` lug pogrooveto positively restrain said parts against relative rotation, a punchedand stamped sheet metal plate, said plate being bent to provide alongitudinallysplit shaft of substantially cylindrical form, said shafthaving a lug struck outwardly therefrom adjacent to said split andengageable with the upper end of said bushing to. insure exposure of agiven length of the Vupper end portion of said shaft, said shaft havinga boss formed thereon in a plane above the aforementioned lug and anotch extending downwardly from the upper edge thereof, a moldedinsulating knob having a recess to accommodate the upper end of saidshaft, said knob having a notch in the lower edge thereof forcooperation with said lug to guide said parts into proper telescopicengagement with each other, the wall of said recess having a depressionformed therein to accommodate said b oss whereby said parts are engagedwith a snap'action, the wall of said recess also having a projectionformed integrally therewith for cooperation with the notch in saidshaft, whereby said knob and said shaft are positively restrainedagainst rotation other, said shaft having a pair of lugs formedintegrally with thel lower end thereof and adapted to extend below saidbushing, a iiat punched plate of insulation having openings toaccommodate said lugs and over the lower surface of which restrain saidshaft and said bushing against substantial movement longitudinally ofeachother, a resilient contactor located upon the lower surface of saidplate having an end portion thereof secured to said plate the notch insaid shaft,

lower end portion inserted I upset over the inner surrelatively to eachsubstantially' centrally of the naar, the free end of said contactorbeing bent downwardly from said plate and having a pair of upwardlyextending substantially parallel ears, and said plate having a notch toaccommodate said ears.

12. In a rheostat-for control of relatively low voltage circuits, incombination, an inverted cupshaped sheet metal housing, an externallythreaded metal bushing secured to the upper end of said housing andhaving a passage communicating with the interior of the latter, alongitudinally split tubular shaft formed of stamped sheet metal, saidshaft being insertable downwardly into said bushing and having aprojection engageable with the upper end of the latter to insureexposure of a given portion of the upper end of said shaft, a hollowmolded insulating knob telescopically engaged with the upper end of saidshaft and positively interlocked therewith against rotation relativelythereto, said knob and said shafthaving parts formed integrallytherewith to provide a snap catch therebetween upon telescoping thereof,said shaft having a plurality of lugs formed integrally with the lowerend thereof, a flat punched plate of insulation having openings throughwhich said lugs extend, said lugs being bent over the lower surface ofsaid plate to rigidly secure the same and said shaft and bushing inassembled relation to each other, a flat metal ring interposed betweensaid plate and the lower end of said bushing, said ring having notchesformed therein and with the walls of which said lugs are adapted toengage to insure a proper electrical connection between said shaft andsaid bushing, and said shaft being formed interiorly to provide forcooperative engagement therewith of the screw shell contact of anelectric lamp.

13. In a rheostat for control of relatively low voltage circuits,iii-combination, an inverted cupshaped sheet metal housing, anexternally threaded metal bushing secured to the upper end of saidhousing and having a passage communicating with the interior of thelatter, a longitudinally split tubular shaftv formed of stamped sheetnietal, said shaft being insertable downwardly into said bushing andhaving a projection engageable with the upper end of the latter toinsure exposure of a given portion of the upper end of said shaft, ahollow molded insulating knob telescopically engaged with the upper endof said shaft and positively interlocked therewith against rotationrelatively thereto, said knob and said shaft having parts formedintegrally therewith to lprovide a snap catch therebetween upontelescoping thereof, said shaft having a plurality of lugs formedintegrally with the lower end thereof, a fiat punched plate ofinsulation having openings through which saidlugs extend, said lugsbeing bent over the lower surface of said plate to rigidly secure thesame and said shaft and bushing-in assembled relation to each other,said shaft having lugs struck inwardly therefrom in vertically andangularly spaced relationship to each other, an electric lamp the screwshell contact of 4which is adapted for cooperative engagement with saidlugs, the major portion of the length of the lamp bulb being positionedwithin the upper end of said shaft, the diameter of said vscrew shelllamp contact being substantially less than the diameter of said lampbulb, and said shaft having a plurality of angularly spaced ribs formedon the inner surface thereof adjacent to said screw shell contact topositively insure substantial centering of the latter.

14. In a rheostat for control .of relatively low voltage circuits, incombination, an inverted cupshaped sheet metal housing, an externallythreaded metal bushing secured to the upper end of said housing andhaving a passage communicating with the interior of the latter, alongitudinally split tubular shaft formed of stamped sheet metal, saidshaft being insertable downwardly into said bushing and having aprojection engageable with the upper end of the Alatter to insureexposure of a given portion of the upper end of said shaft, a hollowmolded insulating knob telescopically engaged with the upper end of saidshaft and positively interlocked therewith against rotation relativelythereto, said knob and said shaft having parts formed, integrallytherewith to provide a snap catch therebetween upon telescoping thereof,said shaft having a plurality'of lugs formed integrally with the lowerend thereof, a. flat punched plate of insulation having openings throughwhich said lugs extend, said lugs being bent over the lower surface ofsaid plate to rigidly secure the same and said shaft and bushing inassembled relation to each other, said shaft having lugs struck inwardlytherefrom in vertically and angularly spaced relationship to each other,an electric lamp the screw shell contact of which is adapted forcooperative engagement with said lugs, the major portion of the lengthof the lamp bulb being positioned within the upper end of said shaft,the inside diameter of said shaft being substantially greater than thediameter of said screw shell lamp contact and said shaft having aplurality of angularly spaced ribs formed on the inner surface thereofadjacent to said screw shell contact to positively insure substantialcentering of the latter, a resilient center lamp contact and a rheostatcontactor respectively positioned upon the upper and lower surfaces ofsaid plate and an eyelet forming an electrical and mechanical connectiontherebetween, an insulating base secured to said housing, a helicallywound resistor interposed between said base and said contacter, and

`a wiring terminal element exposed upon the lower surface of said baseand electrically connected to one end of said'resistor, said contactorbeing movable selectively into and out of engagement with said resistorat the aforementioned end of the latter. i

15. In a rheostat for control of relatively low voltage circuits, incombination, an inverted cupshaped sheet metal housing, an externallythreaded metal bushing secured to the upper end of said housing andhaving a passage communicating with the interior ofthe latter, alongitudinally split tubular shaft formed of stamped sheet metal, saidshaft being insertable downwardly into said bushing and having aprojection engageable with the upper end of the latter,

and said shaft having'parts formed integrally li;

therewith to provide a snap catch therebetween upon telescoping thereof,said shaft having a plurality of lugs formed integrally with the lowerend thereof, a flat punched plate of insulation having openings throughwhich said lugs extend, 1135i eaidlugs being bent over the lower surfaceof said plate to rigidly secure the same and said shaft and bushing inassembled relation to each other, said shaft having lugs struckinwardlytherefrom m verucauy and amaai-1y spaced reis; l

lationship to each other, an electric lamp the screw shell contactofwhich is adapted for cooperative engagement with said lugs, the majorportion of the length of the lamp bulb being positioned within the upperend of said shaft, the inside diameter of said shaft being substantiallygreater than the diameter of said screw shell lamp contact and saidshaft havinga plurality of angularly spaced ribs formed on the innersurface thereof adjacent to said screw shell contact to positivelyinsure substantial centering of the latter, a resilient center lampcontact and a rheo- `stat contactor respectively positioned upon theupper and lower surfaces of said plate and an eyelet forming anelectrical and mechanical connection therebetween, an insulating basesecured to said housing, a helically wound resistor interposed betweensaid base and said contactor, a wiring terminal element exposed upon thelower surface of said base and electrically connected to one end of saidresistor, said contactor being movable selectively into and out ofengagement with said resistor at the aforementioned end of the latter, asecond wiring terminal element exposed upon the lower surface of saidbase, means comprising a resilient metallic member electricallyconnected with said second terminal element and interposed between saidbase and said plate, said member having one arm thereof biased intoengagement with said eyelet, said member also having another arm thereofreiiexed and biased into the'plane of said plate, said last mentionedarm having a boss, and said plate having a pair '.of adjacent peripheralnotches to be releasably engaged by said boss, said notches and saidboss beingutilized to indicate' to the touch the circuit making andcircuit breaking positions respectively of said contactor.

16. In a rheostat for controlling relatively low voltage circuits, incombination, an inverted substantially cup-shaped sheet metal shell, anexternally threaded hollow metal bushing secured to the upper end ofsaid shell, a longitudinally split substantially cylindrical shaftformed of sheet metal, said shaft being insertable downwardly into saidbushing and having a projection engaging theupper end of the latter, ahollow molded insulating knob telescopioally engaged with the upper endof said shaft, said knob and.

said shaft having parts formed integrally there- 'with to provide areleasable snap connection therebetween and to positively restrain thesame against rotary movement relatively to each other, a fiat plate ofinsulation rigidly connected to the lower end of said shaft topositively restrain the latter against separation from said bushing, aninsulating base adapted to seat against the lower end of said shell,said shell having lugs bent inwardly over the lower surface of said baseto secure said parts to each other, a helically wound resistor wirearranged arcuately upon the upper surface of said base and having theends thereof secured to the latter, a wiring terminal element exposedupon the lower surface of said base and electrically connected to oneend of said resistor, a contactor secured to said plate and biased intothe plane of said resistor, said contactor being movable respectivelyinto and out of engagement with said resistor at a point adjacent to thepoint of connection of the aforementioned end thereof to said terminalelement, a second terminal element exposed upon the lower surface ofsaid base, means including a resilient arm associated with said lastmentioned terminal element for continuously electrically connecting theArelatively translucent -end wall of said knob latter with saidcontactor, said plate having a pair of notches formed therein adjacentto each other, and means also associated with said last. mentionedterminal element and biased into engagement with said plate, said meanscooperating with the walls of sai'd notches to indicate to the touch the.movement of said contactor into and/or out of engagementwith saidresistor.

17. In a device of the character described, in combination, a contactoractuating metal shaft of hollow substantially cylindrical form, theinterior of said shaft being formed to provide a screw socket for thescrew shell contact of a lamp, a lamp having the screw shell contactthereof mechanically engaged with and electrically connected to saidshaft, the major portion of the lamp bulb being located within saidshaft, a hollow molded insulating knob adapted to telescopically engagethe upper end of said shaft, said knob and said shaft having partsformed integrally therewith to provide a snap catch therebetween upontelescoping thereof' and to positively restrain the same againstrotation relatively to each other, said knob being composed entirely ofrelatively translucent material, and at least a portion of the upper endwall thereof having a relatively small dimension in vertical section,whereby the lighted or unlighted condition of said lamp is renderedapparent notwithstanding complete enclosure of the latter. l

18. In combination, a tubular metal actuating shaft for rheostats andthe like, an electric lamp insertable into the upper end of said shaftand having a portion of the bulb projecting upwardly beyond and exposedwith respect to the latter, a hollow molded insulating knob removablyattached to the upper end of said shaft and adapted to provide a manualoperating element for the latter, said knob being composed entirely ofmaterial, and the 'upper 115 having adjacent areas of relatively thickand relatively thin cross section respectively, said area of relativelythick cross section being adapted to embody a suitable design which isthrown into accentuated relief with respect to said relatively thin areaunder the influence of light generated in said lamp.

19. In a device of the character described, in combination, an invertedcup-shaped sheet metal housing, an externally threaded metal bushing 125secured to the upper end of said housing and having a passagecommunicatingwith the interior of the latter, a tubular metal shaftinsertable downwardly into said bushing and having an integralprojection engageable with the upper end 13a of the later to insureexposure of a given portion of the upper end of said shaft, said shafthaving a pair of diametrically opposed vertical lugs formed integrallywith the lower end thereof, a fiat punched plate of insulation ofgreater diam- 135 eter than the lower end -of said bushing, said platehaving a pair of openings formed therein and through which said lugsextend, said lugs being bent over the lower surface of said plate torigidly secure the same and said shaft and MG bushing in assembledrelation to each other, a contactor rigidly and permanently attached tosaid plate for support and rotation thereby, said plate having a pair ofradial shoulders formed in 145 the periphery thereof at opposite sidesrespectively of said contactor, and said housing having a lug formedintegrally therewith and extending downwardly into the path of saidshoulders to limit said plate to ,rotation through an angle ofsubstantially less than three hundred and sixty degrees.

20. In a device of the character described, in combination, an invertedcup-shaped sheetmetal 5 housing, an externally threaded metal bushingsecured to the upper end of said housing and having a passagecommunicating with the interior of the latter, a longitudinally splittubular shaft formed of stamped sheet metal, said shaft being insertabledownwardly into said bushing and having a projection engageable with theupper end of the latter to insure exposure of a given portion of theupper end of said shaft, a hollow molded insulatingknob, said knob andsaid shaft having parts formed integrally therewith to provide areleasable snap connection therebetween upon telescoping thereof and topositively restrain the same against rotation relatively to each other,said shaft havint a pair of diametrieally opposed lugs formed mtemuywith the lower end thereof, a flat pimched plate of insulation ofgreater diameter than the lower end of said bushing, said plate havingopenings formed therein and throush which said lugs extend, said lugsbeing bent over the lower surface of said plate to rigidly securel.ALVIN W. KRIEGER.

